Police in Arizona are hunting for a gunman who killed at least three people, including a forensic psychiatrist who worked on high-profile murder cases. Dr. Steven Pitt, who assisted with the infamous JonBenét Ramsey investigation, was shot and killed last Thursday. Police linked the killing with the murders of two paralegals the next day. With a fourth murder in three days, the city is desperate for answers. Mireya Villarreal reports. Subscribe to the "CBS This Morning" Channel HERE: http://bit.ly/1Q0v2hE Watch "CBS This Morning" HERE: http://bit.ly/1T88yAR Watch the latest installment of "Note to Self," only on "CBS This Morning," HERE: http://cbsn.ws/1Sh8XlB Follow "CBS This Morning" on Instagram HERE: http://bit.ly/1Q7NGnY Like "CBS This Morning" on Facebook HERE: http://on.fb.me/1LhtdvI Follow "CBS This Morning" on Twitter HERE: http://bit.ly/1Xj5W3p Follow "CBS This Morning" on Google+ HERE: http://bit.ly/1SIM4I8 Get the latest news and best in original reporting from CBS News delivered to your inbox. Subscribe to newsletters HERE: http://cbsn.ws/1RqHw7T Get your news on the go! Download CBS News mobile apps HERE: http://cbsn.ws/1Xb1WC8 Get new episodes of shows you love across devices the next day, stream local news live, and watch full seasons of CBS fan favorites anytime, anywhere with CBS All Access. Try it free! http://bit.ly/1OQA29B Delivered by Norah O’Donnell and Gayle King, "CBS This Morning" offers a thoughtful, substantive and insightful source of news and information to a daily audience of 3 million viewers. The Emmy Award-winning broadcast presents a mix of daily news, coverage of developing stories of national and global significance, and interviews with leading figures in politics, business and entertainment. Check local listings for "CBS This Morning" broadcast times.